The present invention relates to a motor vehicle navigation method and system. More specifically, the system according to the invention is intended to assist with the travel of a vehicle through a predetermined geographical zone.
Navigation systems which allow a driver to navigate through a predetermined zone are already known. These systems display on a screen the major maneuvers that have to be performed in order to reach an objective set by the driver. In general, such systems operate as follows:
the driver initially defines an objective to be reached,
the system calculates and establishes a favored route for reaching it, and
the system guides the driver step by step until this objective is reached.
Guidance is performed using voice messages and/or a screen placed on the vehicle dashboard. Conventionally, the screen displays directional pictograms indicating to the driver the major maneuvers that he has to reproduce in order to reach the set objective.
Document DE 39 05 493 (BOSCH) describes a navigation system which displays a detailed road map on a screen on board the vehicle. However, this road map is difficult to consult quickly when a decision as to which direction to take is needed. According to that patent, the driver then has the option of requesting simplified guidance. This simplified guidance gives him a direction indication of the type shown on road signs, instead of the detailed road map. The purpose of such simplified guidance is to assist the driver in quickly making a decision. However, this guidance does not reflect the actual topography of the area because the road infrastructure is depicted symbolically. Thus, for example, if the driver needs to follow a main road which turns to the right, the simplified display will display xe2x80x9ccontinue straight onxe2x80x9d, because what is needed is to continue following the main road. This may of course cause the driver to make a mistake or at the very least may trouble him. The simplified guidance mode according to that patent is unable to resolve such directional ambiguities.
Likewise, document U.S. Pat. No. 5,544,060 (ZEXEL) describes a navigation system equipped with a preview function. Such a system, in addition to the conventional display of a direction indication, allows the display of all the direction indications that will be given to the driver during the journey he has to make to be requested at any moment on the journey. This preview function does not, however, give the driver any additional information when he does not understand a direction indication asking him to continue straight on (because he needs to follow the main road) when the road before him is turning. Such a navigation system does not allow the ambiguity felt by the driver in such a scenario to be removed.
Now, this scenario (a divergence between an indication given by the navigation system and the actual layout of the area as seen by the driver) occurs fairly often. This is because the mapping available commercially at the present time is often incomplete, or even incorrect, both in built-up areas and in rural areas. In built-up areas, the errors are mainly due to new roads which are not shown on the maps, or to modifications to the traffic plan. In rural areas, not all of the secondary roads are shown on the map and the risk of error is therefore great. The indications given by the screen may sometimes cause the driver to make a mistake. Thus, as was explained earlier, when the main road turns to the right or to the left, the navigation system depicts the direction to be taken as a xe2x80x9cstraight onxe2x80x9d indication. This is because, as far as the system is concerned, as it is still the main road that has to be followed, it is the xe2x80x9cstraight onxe2x80x9d direction that has to be taken. If, through ill fortune, in the bend in the main road, there is a road leading xe2x80x9cstraight onxe2x80x9d which is either not on the map or looks to be of the same order of importance even thought it has been mapped with a lower order of importance, there is the risk that the driver will take the wrong direction. Such mapping errors and/or guidance anomalies are relatively frequent.
In order to alleviate this type of fault, it is already known practice, when the driver requests it, for the navigation device screen to display not only guidance pictograms indicating the major changes in direction to be taken, but the stored map of the point at which the vehicle is located. However, for the screen to be able to display such a map it has to be large enough and have a high resolution. A screen of this type is therefore relatively expensive. Furthermore, this solution has the major drawback of requiring the driver to analyze a map while he is driving, which may be prejudicial to safety or require him to stop the vehicle, still for safety reasons.
The present invention proposes a motor vehicle navigation system which easily guides a driver when he detects an ambiguity and does so without presenting a detailed map on the screen and without requiring the driver to have to interpret such a map.
To this end, the present invention relates to a motor vehicle navigation system, of the type comprising:
a central navigation computation unit equipped with a memory containing actual topographical data of a predetermined zone, and
a device for locating the vehicle, the central unit being associated with a voice-guidance device and/or with a screen operating in a mode known as xe2x80x9cnormal guidancexe2x80x9d mode, in which at least one direction pictogram is displayed on the screen to indicate the major maneuvers which have presently to be reproduced by the driver, said system being characterized in that it further comprises:
a control designed to make the voice-guidance device and/or the screen operate in a temporarily enhanced guidance mode, in which at least one voice message and/or one direction pictogram reproduces the topography, as stored, of the area for which enhanced guidance has been requested, said enhanced guidance pictogram and/or the associated voice message being obtained by temporary modification of the filtering applied to the stored topographical data.
A system of this kind therefore allows the driver to have before him a simplified form of the map depicting the topography of the area on the screen. This map displays only pictograms reproducing the stored geographical configuration of the road infrastructure at the predetermined point. This actual geometric configuration may possibly be simplified slightly, but not interpreted. Thus a bend to the right by 15.5xc2x0 (for example) will not necessarily be depicted exactly by an arrow to the right inclined by 15.5xc2x0, but the bend to the right will be shown. In contrast, this same bend to the right will not be interpreted as having to be shown by a xe2x80x9cstraight onxe2x80x9d arrow, under the pretext that it is the main road which is turning to the right.
Thus, if a main road turns to the right whereas the voice-synthesis device and the normal guidance display indicates to continue straight on, the enhanced guidance mode announces that the main road turns and presents a pictogram reproducing the direction of this road as stored in memory. By virtue of the enhanced guidance requested by the driver, the ambiguity is removed and the driver knows that the main road turns, which allows him to continue in the right direction.
This enhanced guidance is displayed on the screen by a temporary modification to the filtering of the data that is to be displayed. This modification to the filtering is limited in space and/or in time.
Advantageously, according to the invention, the control which allows the driver to request temporary enhanced guidance may be a push-button placed as close as possible to the driver or be a device controlled by voice or any other similar means.
It will also be noted that the enhanced guidance requested ceases automatically as soon as the vehicle has performed the maneuver indicated by the pictogram.
The end of enhanced guidance mode may also be automated by a time delay and occur when a certain amount of time has elapsed.
The present invention also relates to a navigation method which employs the above-described device.
Further objects, features and advantages of the present invention will in any event emerge from the description which follows by way of nonlimiting example and with reference to the appended drawings, in which: